Many types of input devices are available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch sensor panels, joysticks, touch pads, touch screens, and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned behind the panel so that the touch sensitive surface can substantially cover the viewable area of the display device. Touch screens can generally allow a user to perform various functions by touching or near touching the touch sensor panel using one or more fingers, a stylus or other object at a location dictated by a user interface (UI) including virtual buttons, keys, bars, displays, and other elements, being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
Touch screens that integrate touch circuitry with display circuitry are described in U.S. patent application Ser. No. 11/760,080, entitled “Touch Screen Liquid Crystal Display,” and Ser. No. 12/240,964, entitled “Display with Dual-Function Capacitive Elements,” the contents of which are incorporated herein by reference in their entirety for all purposes. In these touch screens, display pixels can be grouped into drive regions to receive a stimulation signal and sense regions to transmit a touch signal based on a touch or near touch. These regions can generally be disposed in a rectangular configuration with, from left to right, some drive regions aligning vertically, a sense region extending vertically along the lengths of the drive regions, more drive regions aligning vertically, another sense region extending vertically along the lengths of the drive regions, and so on.
Because of this rectangular configuration, horizontal drive lines for transmitting the stimulation signal and vertical sense lines for transmitting the touch signal can cross numerous times in the sense regions, creating parasitic capacitance that can interfere with the ability of the touch screen to effectively sense the touch or near touch. However, to reduce the effects of this parasitic capacitance, more expensive and powerful sensing circuitry may be needed to improve the signal-to-noise ratio of the touch signal.